Elastic-fluid turbine



ELASTIC FLUID TURBINE} Filed Sept. 26, 1955 7 Sheets-Sheet l Jan. 5, 1937 F. LOSS ELASTIC FLUID TURBINE 7 Sheets-Sh et 2 Filed Sept. 26, '1935 INVENTQR Y A a? f ATT'O RNEY Jan. 5, 1937. L ss 2,066,410

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/\ INVE NTOR ATTORNEYS Patented Jan. 5, 1937 UNITED STATES PATENT OFFICE signor to The Parsons Marine Steam Turbine Company Limited, Wallsend-on-Tyne, England Application September 26, 1935, Serial No. 42,254 In Great Britain October 5, 1934 6 Claims. (Cl. 253-69) This invention relates to elastic-fluid turbines and particularly to impulse turbines or stages.

In many applications of turbines, particularly in marine Work, it is necessary that they should operate at both high and low powers and in order to obtain a reasonable efficiency at both such powers, it has been proposed to use a turbine impulse wheel as a two-row wheel at low powers and as a single-row wheel at high powers by omitting the guide blades between the two moving rows in that part of the periphery opposite the full-power nozzles placed, like the lowpower nozzles, immediately in front of the first row of blades.

That this arrangement is adapted for meeting the different conditions of working will be understood from the consideration that if the initial pressure is maintained in the nozzle box, as isusual, the pressure drop across the nozzles, and consequent1y the velocity of the steam, is considerably greater at low power than at full power so that velocity compounding is desirable at the lower .powers.

For example, if the velocity ratio of an im- -pulse turbine, that is to say, the ratio of the circumferential velocity of the turbine blades to the velocity of the steam issuing from the nozzles, at full power is in the neighbourhood of .5, maximum efiiciency can be obtained by using a single row of moving blades. If at lower powers, the velocity ratio falls to the neighbourhood of .25, maximum efiiciency can be obtained with two moving rows, while if the velocity ratio falls to the neighbourhood of .125, maximum efficiency is obtained with three moving rows.

The main object of the present invention is to provide improved impulse turbines or stages of the kind indicated having advantages as hereinafter set forth.

With this object, the present invention consists in an elastic-fluid impulse turbine stage comprising the combinations of elements hereinafter described and particularly pointed out in the claims.

Referring to the accompanying diagrammatic drawings:

Figure 1 is a section through part of the fullpower section of one form of impulse stage of a steam turbine embodying the present invention. 5 Figure 2 is a developed circumferential section through the line 2-2 of Figure 1.

Figure 3 is a section through part of the lowpower section of a modified form of impulse 65 stage.

employed with the arrangement of Figures 7 and 8.

Figures 10 and 11 are views similar to Figure 1 but in respect of a three-row, blade modification employing highand low-power nozzle means.

Figures '12, 13 and 14 are views similar to Figures 10 and 11 but in respect of a, modification having high-, lowand intermediate-power nozzle means, and

Figure 15 is a developed view of the disposition of nozzles and blades for high, intermediate and low powers shown as sections taken respectively on the lines l2-I2, |3l3, and l4l4 of Figures 12, 13 and 14. i

In carrying the invention into effect according to one form illustrated in Figures 1 to 4 as applied to a steam turbine, an impulse wheel a is provided having two rows of moving blades b, c of different length spaced a sufiicient distance apart axially to accommodate nozzles d for fullpower working between them, these nozzles which alone are operative at full power being arranged over only a limited sector of the periphery in front of the second or longer set of blades 0 in the direction of flow of the steam, as shown in Figure 15 in relation to a modified form of the invention described below.

At low powers, steam issues from other nozzles e arranged over a sector (see Figure 15) of the periphery other than that occupied by the fullpower nozzles d and placed behind the first or shorter set of moving blades 1); after passing through this first set b, the steam is directed by guide blades 1 to the second set c of moving blades so that velocity is extracted in two stages.

The guide blades 1 are provided with shrouds g (Figures 3 and 4) of considerable length axially to lead the steam over the considerable space between the first and second rows of blades.

Alternatively as in Figures 5 and 6, with the same object, the guide blades f may be of greater breadth than usual.

In the arrangement described with reference to Figures 1 to 6, the two rows of blades b, c are mounted on parts of the turbine-wheel periphery of substantially the same diameter, but according to a modified form, illustrated in Figures 7 to 9, the blades 0 associated with the full-power nozzles d are arranged on a part of the wheel (11 of greater diameter, so that the full-power nozzles (1 may axially overlap the first row of blades 1) to a certain extent and the two rows may working with appropriate intermediate guide blades I, I1 so that at full power, steam. passes through only the third row of blades 0 whilst.

at low power, steam passes successively through the first, second and third rows of blades.

Instead of providing nozzles d, e for only highpower and low-power working respectively, nozzles'h may be provided as indicated in'Figure 13 for intermediate power in addition, the vfullpower nozzlesd, which are disposed between the second and third rows of blades, directing steam on the third row alone (Figure 12), while the intermediate-powernozzles h, disposed between the first and second rows, direct steam through the second and third rows, and finally, the lowpower nozzles e which are placed immediately behind the first row (Figure 14), provide steam to pass in series through the first, second and third rows of moving blades, intermediate guide blades 1, f1 being provided as before.

The relation-of the high, intermediate and lowpressure nozzles in different limited segments is shown in Figure 15.

Impulse wheels constructedin accordance with {the present invention. enable a high efficiency to be maintained over a widerange of power conditions.

3 It will be'seen that in all conditions of working,

steam leaves the final row of impulse blades, and consequently has a free'path to any following stages of the turbine, while the maximum blade height is that necessary for the full-power single-row conditions. V

This latter feature ensures that at all powers,

the windage losses of the inoperative blades are small as compared with known constructions in l Although various constructional forms of the invention have been described in considerable detail in order to make clear its general nature,

-it will be understood that many variations can be made to suit different conditions of working and different types of turbine without exceeding the scope of the invention. I

I claim:

1. An elastic-fluid impulse turbine stage, comprising in combination, nozzle meansfor generating velocity in a jet of: elastic fluid in certain working conditions and means for abstracting velocity so generated, said abstracting means including at least two spaced rows of one-tier rows of runningblades, Iorabs'tracting velocity so generated.

2. An elastic-fluid impulse Y turbine stage as claimed in claim 1, in which nozzle means operative in relation to one of said rowsofrunning blades and guideblades directing elastic fluidf to another row of said running blades are arranged over functionally corresponding sectors. 3. An elastic-fluid impulse turbine stage as claimed in claim 1', in'which said-nozzle means and said other nozzle-imeans disposed in said space occupy difierent sectora 4. An elastic-fluid impulse turbine stage as claimedin claim 1, in "which said-"guide blades spaces I I I 5. An elastic fluid impulse turbine stage'as V claimed in claim 1, in which said spaced rows of running blades are in stepped formation to assist 1 in providing accommodation" for said nozzle means disposed insaidspace. 1

6. An elastic-fluid impulse 'turbines'tage: as.

claimed in claim 1, in which said guidebladea are'of the same'width as said running blades but are of substantially less width than that or" said space in which they are disposed; together with a plurality of shrouding strips carried by each of said guide blades and projecting on each side thereof to assist in leadingelastic fluid-across said space. 

